By. RADIATION & PREGNANCY Diagnostic & Therapeutic procedures causing exposure of the abdomen of...

RADIATION & PREGNANCY

RADIATION & PREGNANCY

Diagnostic & Therapeutic procedures causing exposure of the abdomen of women likely to be pregnant should be avoided unless there is a strong clinical indications

STOCHASTIC STOCHASTIC

EFFECTSEFFECTS

STOCHASTIC EFFECTSSTOCHASTIC EFFECTS

Stochastic Effects are caused by mutations in a cell or in small group of cells


The absorbed dose is not important for severity of the effect, but for probability of the effect depend on the absorbed dose


Examples of stochastic effect

malignancies and hereditary effects.

No threshold dose.

DETERMINISTIC EFFECTSDETERMINISTIC EFFECTS


Result from killing of cells.

There is a threshold dose.

e.g.: Fetal death, gross malformation

DETERMINISTIC EFFECTSDETERMINISTIC EFFECTSPre-Implantation: 0 – 8 days post-Pre-Implantation: 0 – 8 days post-conceptionconception

Death of embryo 5 cGy rats

0.9 cGy mice

Threshold dose: 10 cGy


Embryonic = 9 – 60 daysEmbryonic = 9 – 60 days

Risk of embryonic death remain.higher threshold dose.Risk of malformation is in the order of 0.5% per cGyThreshold dose = 10 cGy

Small head size 1% per cGyThreshold dose = 10 – 20 cGyGrowth retardation threshold dose = 5 – 25 cGy


Early fetal = 61 – 104 daysEarly fetal = 61 – 104 days

Threshold dose for lethality = 0.5 Gy

Mental retardation 0.4% per cGyThreshold dose = 12 cGy

0.3 IQ points per cGyUnprovoked seizures 4 – 8 cGy threshold doseAll seizure 11 – 15 cGy threshold dose


Mid fetal = 105 – 175 days post-conceptionMid fetal = 105 – 175 days post-conception

Risk of fetal death remain in this period, but seems to be lower than in the earlier period

Threshold doses

0.65Gy for mental retardation

0.5 Gy for small head size

0.5 Gy for growth retardation

DETERMINISTIC & EFFECTSDETERMINISTIC & EFFECTS

Late fetal = more than 175 days post-conceptionLate fetal = more than 175 days post-conception

Risk of fetal death seem to be low

Risk of malformation & mental retardation are negligible

STOCHASTIC EFFECTS


Excess Fatal CancerExcess Fatal Cancer

Natural prevalence of fatal childhood cancer up to the age of 15-year (1:1300)

0.03% per cGy0.04% - 0.05% cGyHigher risk for those irradiated in the second trimester than those in third trimester

TUMOURSTUMOURS

TUMOURSTUMOURS

Leukemia, tumours of CNS

RISK OF RISK OF GENETIC GENETIC DISEASEDISEASE

NATURAL NATURAL PREVALENCE IS PREVALENCE IS

1.6%1.6%

Maternal age > 35Total chromosal abnormality is 2.26% & 9.6% age above 45

1 cGy 0.012%

It is clear that risk of radiation effects is smaller than risk effect by age

Normal risk that a child will have congenital defect is 3% – 6%

When dose exceed 10 cGy probability increase to 10%

A dose of 10 cGy – 20 cGy is radiologically not accepted as an indication for an abortion

Dose to the embryo of 20 cGy at 3-Weeks could be accepted as a reason for “Therapeutic Abortion”

Whalen & Batter

Dose from Nuclear Medicine Diagnostic test is at’s highest estimate 1 cGy

Threshold dose for deterministic effect is in the order of 10 cGy – 60 cGy

The risk of cancer induction is 0.03% - 0.06% per cGy

If patient received 0.5 cGy

(1.5 – 2.5) out of 10,000

Risk of genetic defect

(0.5 – 5) out of 10,000

ProjectionProjection ExaminationExamination

Estimated Fetal Dose per Examination (mGy)Estimated Fetal Dose per Examination (mGy)

Mean Mean

(this work)(this work)Reported Reported

MeanMeanRange Range

(this work)(this work)Reported RangeReported Range

AP Abdomena 2.9 1.9 0.26 – 15.0 0.16 – 9.2

PA Abdomena 1.3 0.53 0.64 – 3.0 0.35 – 0.82

Abdomenb 2.6 2.5 [1.4] 0.26 – 15.0 0.25 – 19.0 {4.2}

AP Chesta < 0.01 < 0.01 < 0.01 < 0.01

PA Chesta < 0.01 < 0.01 < 0.01 < 0.01

Chestb < 0.01 0.01 [< 0.01] 0.002 – 0.43 < 0.01

AP Lumbar Spinea 7.5 1.9 0.31 – 40.0 0.20 – 15.0

LAT Lumbar Spinea 0.91 0.41 0.09 – 3.5 0.09 – 3.1

Lumbar Spineb 4.2 4.0 [1.7] 0.09 – 40.0 0.27 – 40.0 {10.0}

LAT Lumbosacral Jointa 1.1 0.56 0.10 – 2.03 0.09 – 2.4

AP Pelvisb 3.4 2.0 [1.1] 1.4 – 15.0 0.55 – 22.0 {4.0}

AP Thoracic Spinea < 0.01 < 0.01 < 0.01 < 0.01 – 0.03

PA Thoracic Spinea < 0.01 < 0.01 < 0.01 < 0.01 – 0.01

Thoracic Spineb < 0.01 < 0.1 [< 0.01] < 0.01 < 0.1-0.55 {<0.01}

COMPARISON OF THE ESTIMATED MEAN & RANGE OF FETAL DOSECOMPARISON OF THE ESTIMATED MEAN & RANGE OF FETAL DOSE

a – Reported mean & range are adapted from Shrimpton et alb – Reported mean & range are adapted from Wagner et al

Mean values in square brackets & values curly brackets (representing only maximum values) are adapted from Sharp et al

ProjectionProjection ExaminationExamination

Estimated Fetal Dose per Examination (mGy)Estimated Fetal Dose per Examination (mGy)

Mean Mean

(this work)(this work)Reported Reported

MeanMeanRange Range

(this work)(this work)Reported RangeReported Range

IVU 4.8 6.0 [1.7] 2.9 – 6.8 0.7 – 55.0 {10.0}

Barium Enema 6.1 10.0 [6.8] 0.3 – 10.4 0.28 – 130.0 {24.0}

Barium Meal 1.5 - [1.1] 0.1 – 2.3 - {5.8}

Cholecystography 0.6 1.0 0.08 – 1.1 0.05 – 16.0

AP Urinary Bladder 3.9 0.56 – 11.0


a – Reported mean & range are adapted from Shrimpton et alb – Reported mean & range are adapted from Wagner et al

Mean values in square brackets & values curly brackets (representing only maximum values) are adapted from Sharp et al

ProjectionProjection ExaminationExaminationFetal dose per examination (mGy)Fetal dose per examination (mGy)

RangeRange MeanMean

AP Abdomen 0.26 – 15.0 2.9

PA Abdomen 0.64 – 3.0 1.3

Abdomena 0.26 – 15.0 2.6

AP Chest < 0.01 – 0.01 < 0.01

PA Chest < 0.01 < 0.01

Chestb > 0.01 – 0.01 < 0.01

a – Average for the various projectionsb – For only one examination

MEAN FETAL ABSORBED DOSE PER EXAMINATION (GXR)MEAN FETAL ABSORBED DOSE PER EXAMINATION (GXR)

Contd…

ProjectionProjection ExaminationExaminationFetal dose per examination (mGy)Fetal dose per examination (mGy)

RangeRange MeanMean

AP Hip joint 0.11 – 2.1 0.9

AP Lumbar Spine 0.31 – 40.0 7.5

LAT Lumbar Spine 0.09 – 3.5 0.91

OBL Lumbar Spine 0.61 – 2.0 1.3

Lumbar Spinea 0.09 – 40.0 4.2

LAT Lumbosacral Joint 0.10 – 2.0 1.1

AP Pelvis 1.4 – 15.0 3.4

AP Thoracic Spine < 0.01 < 0.01

LAT Thoracic Spine < 0.01b

Thoracic Spineb < 0.01 < 0.01

a – Average for the various projectionsb – For only one examination

MEAN FETAL ABSORBED DOSE PER EXAMINATION (GXR)MEAN FETAL ABSORBED DOSE PER EXAMINATION (GXR)

ExaminationExamination No. of CasesNo. of CasesFetal dose per examination (mGy)Fetal dose per examination (mGy)

RangeRange MeanMean

Liver 4 2.0 – 4.4 3.6

Lumbar Spine 1 2.8

Lung 2 1.0 – 1.4 1.2

Pelvis 2 65.0 – 114.0 89.0

MEAN FETAL ABSORBED DOSE PER EXAMINATION (CT)MEAN FETAL ABSORBED DOSE PER EXAMINATION (CT)


RadiopharmaceuticalRadiopharmaceuticalConversion factorConversion factor

(cGy/MBq) [1,3](cGy/MBq) [1,3]Activity (MBq]Activity (MBq] Route of Route of

AdministrationAdministrationDose to the Uterus Dose to the Uterus

(cGy)(cGy)

123I-Sodiumiodide 1.4x10-3 20 i.v. 2.8x10-2

123I-MIBG 1.1x10-3 30 i.v. 3.3x10-2

131I-MIBG 8.0x10-3 300 i.v. 2.4

67Ga-citrate 7.9X10-3 150 i.v. 1.18

201Tl-chloride 5.0x10-3 100-150 i.v. 5-7x10-1

99mTc-tetrofosmin

(1-day protocol, rest)8.4x10-4 150 i.v. 1.3x10-1

99mTc-tetrofosmin

(1-day protocol, effort)7.3x10-4 450 i.v. 3.3x10-1

MIBG, Metaiodobenzylguanidine; MDP, methylene diphosphonate; HDP, hydroxydiphosphonate; MAA, macroaggregated albumin; MAG3, mercaptoacetyltriglycine


RadiopharmaceuticalRadiopharmaceuticalConversion factorConversion factor

(cGy/MBq) [1,3](cGy/MBq) [1,3]Activity (MBq]Activity (MBq] Route of Route of

AdministrationAdministrationDose to the Uterus Dose to the Uterus

(cGy)(cGy)

99mTc-sestamibi

(1-day protocol, rest)7.8x10-4 150 i.v. 1.2x10-1

99mTc-sestamibi

(1-day protocol, effort)7.2x10-4 450 i.v. 3.2x10-1

99mTc-MDP 6.1x10-4 400 i.v. 2.4x10-1

99mTc-HDP 6.1x10-4 400 i.v. 2.4x10-1

99mTc-MAA 2.4x10-4 100 i.v. 2.4x10-2

81mKr-gas 6.0x10-8

(per minute)

Generator:

450-750 MBq/minuteInhalation < 10-3

99mTc-MAG3 1.2x10-3 40 i.v. 4.8x10-2

MIBG, Metaiodobenzylguanidine; MDP, methylene diphosphonate; HDP, hydroxydiphosphonate; MAA, macroaggregated albumin; MAG3, mercaptoacetyltriglycine

131131I-Therapy I-Therapy &&

PregnancyPregnancy

131131I-Therapy & PregnancyI-Therapy & Pregnancy

10 – 12 Weeks thyroid gland of fetus start to function.

For every 10mCi the mother receive, the fetus will receive

1 cGy.

.

Radiation Worker’s & PregnancyRadiation Worker’s & Pregnancy

Radiation worker who is pregnant should not

receive more than 1 mSv during the whole

pregnancy.

CONCLUSIONCONCLUSION

CONCLUSIONCONCLUSION

For diagnostic examination whether radiological or Nuclear Medicine, the risks for the fetus are

Extremely low

For therapeutic dose•The doses may be high enough to cause unacceptable tissue damage.

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